1,721,478 research outputs found
Bulk rock geochemistry and zircon analysis: a combined tool to compare meta-sedimentary units.
No full textSulla variabilità compositiva delle miche nell'ambito dello stesso affioramento di metapeliti di basso grado: un esempio. 1:Le biotiti.
No full textSulla variabilità compositiva delle miche nell'ambito dello stesso affioramento di metapeliti di basso grado: un esempio. 2: Le muscoviti e considerazioni conclusive. Rend. Fis. Acc. Lincei, IX, 3, 1, 43-55.
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Manganese-containing inclusions in late-antique glass mosaic tesserae: A new technological marker?
Full text linkThe present study focuses on manganese-containing inclusions identified in late-Antique glass tesserae, light brown/amber and purple in colour, from Padova (Italy), in order to clarify the nature of these inclusions, never identified in glass mosaics until now, and provide new insights on the production technologies of such kinds of tesserae. Multi-methodological investigations on manganese-containing inclusions were carried out in this work by means of optical microscopy (OM), scanning electron microscopy (SEM), micro-X-ray diffraction (micro-XRD), electron backscattered diffraction (EBSD), electron microprobe (EMPA), and micro-Raman spectroscopy. The combination of analytical results shows that inclusions are crystalline, new-formed phases, mainly composed of manganese, silica and calcium, and are mineralogically ascribed as a member of the braunite-neltnerite series, with unit-cell parameters closer to those of neltnerite. However, the low Ca content makes such crystalline compounds more similar to braunite, in more detail, they could be described as Ca-rich braunite. The occurrence of such crystalline phase allows us to constrain melting temperatures between 1000 and 1150 °C, and to hypothesize pyrolusite, MnO2, as the source of manganese. In addition, it is worth underlining that the same phase is identified in tesserae characterised by different colours (light brown/amber vs purple due to different manganese/iron ratios), glassy matrices (soda-lime-lead vs soda-lime) and opacifiers (cassiterite vs no opacifier). This suggests that its occurrence is not influenced by the chemical environment, revealing these manganese-containing inclusions as a new potential technological marker
A microstructural and compositive SEM study of melt inclusions in orthopyroxene (Bajo Pobre Formation, Argentina)
No full textSimulating the Growth of Garnet Porphyroblasts using a Diffusion-Limited Aggregation Model
No full textThe effect of prolonged heat treatments on the microstructural evolution of Al/Ni intermetallic compounds in multi layered composites
No full textn this work the effects of prolonged heat treatments on the microstructural and crystallographic evolution of Al-Ni intermetallic compounds were studied in Al/Ni multilayer samples, produced by accumulative roll bonding (ARB) process. Starting from aluminium and nickel sheets, the stacks were composed alternating three aluminium with two nickel sheets. After six rolling passes, the roll-bonded material was heat treated in a tubular furnace at 500, 550 and 600 °C for different times (1-20 h). The ARB process followed by the diffusion heat treatments allowed the formation of four Al-Ni intermetallic phases (Al3Ni, Al3Ni2, AlNi and AlNi3). Microstructural analyses of the obtained samples were carried out by scanning electron microscopy (SEM). The electron backscattered diffraction (EBSD) technique was used for the crystallographic analysis of the samples. After the prolonged annealing, three different sequences of phases, starting from Al, were observed: Al3Ni2-AlNi-AlNi3, Al3Ni and AlNi-Al3Ni. The EBSD analysis showed that the intermetallic phases grew with a mean grain size between 0.5 μm and 3 μm and without a preferential crystallographic orientation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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